This invention relates to an electric heater with a sensor for preventing no-water heating, particularly to one provided with a water level probe, a sensing electrode for detecting the water level stored in a water tank on a heater so as to automatically cut off power of an electric heating film, enhancing safety in use of an electric heating appliance.
An electric oven disclosed in a Taiwan patent application of publication number 301523 includes a heater made of micro-crystal plane glass coated with a heating film on a lower surface of the glass for producing heat. But it has a drawback of possible cracking by external force, leading to water or electricity leakage and subsequent danger to the user.
Another Taiwan patent application of publication number 319373 entitled xe2x80x9cWater heater provided with a heating filmxe2x80x9d includes a heating chamber made of insulating material, and a heating film provided in the heating chamber, and the insulating material is made of micro-crystal glass, which has the same problem and drawback as the case of No. 301523.
Another Taiwan patent application of publication number 509453 entitled xe2x80x9cElectric heating discxe2x80x9d includes a heat-transmitting disc, a heating film member, heat-insulating cotton, and a frame plate. The heating film member produces heat to be transmitted to the heat-transmitting disc, and is made of an electric heating tube or piece, with the heat-transmitting disc indirectly heated up, this kind of heating disc has inferior heat efficiency.
Another Taiwan patent application of publication number 427500 entitled xe2x80x9cHeating plate of an electric heaterxe2x80x9d includes a heating plate made of porcelain, glass and steel and coated with enamel, and a tubular or plate heater is placed in the heating plate, which has the problem of inferior heat efficiency.
The objective of the invention is to offer an electric heater with a sensor for preventing no-water heating, by means of automatic cutting off power of the electric heating film with provision of a water level sensor, so as to enhance the safety in using an electric heating appliance.
The invention has the following features.
1. An electric heater with a sensor for preventing no-water heating has a heating plate with its lower surface electro-plated with an electric heating film for producing heat electrically, and the heat is transmitted to and by the heating plate to obtain high heating efficiency.
2. An electric heater with a sensor for preventing no-water heating has a metal plate fixed on the heating plate for strengthening the upper surface of the heating plate.
3. An electric heater with sensor for preventing no-water heating has a water-level probe or a sensing electrode provided on a proper location of the heating plate and extending upward or downward the heating plate to directly detect the water level in a water tank.
An electric heater with a sensor for preventing no-water heating has a temperature sensor and a temperature fuse to perform detection of the water level and controlling of the temperature.